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Following the fitting of my new 3.38 ratio diff to my V8 Hunter I bought a Taylor Made Electronic speedo from Europaspares so that I could calibrate it myself to give exactly the correct speedo reading. I also bought a matching speedo sensor as, according the adverts, it could “simply” be mounted to pick up from the propshaft bolts.
Unfortunately the front diff flange was well hidden by the R380 rear gearbox support which now has my extra front exhaust hangers bolted to it, so use of that that was ruled out.
After removing the rear prop safety plate I discovered that the rear prop flange bolt holes are not equispaced, as required by the sender, but are located at the four corners of a rectangle, so the sender would not give the required symmetrical signal to the speedo. Also the lugs of the universal joint bearings protruded further out than the bolt heads, so they would have hit the sender even if the bolt spacing was correct / useable.
I then noticed that there are four additional plain 10mm holes drilled through the Sierra rear flange. I decided that I could use these for my speedo sensor.
I would like to have used Sel lock pins but none were readily to hand so I cut four 0.75” long pieces from a length of 10mm O/D M/S tubing from B&Q and carefully filed them to be all the same length to preserve prop balance. I used a thin junior hacksaw to slit the tubes down their length and carefully deburred all the edges. By disconnecting the rear prop flange and wedging it up out of the way I used a nylon hammer to tap the tubes through the flange, finishing off with a flat block of dural to ensure they were all flush with the joint flange. A drop of bearing fit was added to each tube before fitting to ensure that the tubes stay put. Photo 1 shows the tubes protruding through the back of the flange.
I made up a bracket in two parts to aid fitting and adjustment. The photo 2 shows the final bracket fitted with the sender in place. The bracket is clamped around the off side spacer on the lower diff mounting bolts. The sender has a clever LED built in so a temporary 12 volt supply was rigged and the sender position adjusted until there were 4 flashes per revolution of the prop. Now for the joy of fitting the speedo! Peter.
Sender Tubes
Sender Tubes.jpg
Sender Bracket
Sender Bracket.jpg
Unfortunately the front diff flange was well hidden by the R380 rear gearbox support which now has my extra front exhaust hangers bolted to it, so use of that that was ruled out.
After removing the rear prop safety plate I discovered that the rear prop flange bolt holes are not equispaced, as required by the sender, but are located at the four corners of a rectangle, so the sender would not give the required symmetrical signal to the speedo. Also the lugs of the universal joint bearings protruded further out than the bolt heads, so they would have hit the sender even if the bolt spacing was correct / useable.
I then noticed that there are four additional plain 10mm holes drilled through the Sierra rear flange. I decided that I could use these for my speedo sensor.
I would like to have used Sel lock pins but none were readily to hand so I cut four 0.75” long pieces from a length of 10mm O/D M/S tubing from B&Q and carefully filed them to be all the same length to preserve prop balance. I used a thin junior hacksaw to slit the tubes down their length and carefully deburred all the edges. By disconnecting the rear prop flange and wedging it up out of the way I used a nylon hammer to tap the tubes through the flange, finishing off with a flat block of dural to ensure they were all flush with the joint flange. A drop of bearing fit was added to each tube before fitting to ensure that the tubes stay put. Photo 1 shows the tubes protruding through the back of the flange.
I made up a bracket in two parts to aid fitting and adjustment. The photo 2 shows the final bracket fitted with the sender in place. The bracket is clamped around the off side spacer on the lower diff mounting bolts. The sender has a clever LED built in so a temporary 12 volt supply was rigged and the sender position adjusted until there were 4 flashes per revolution of the prop. Now for the joy of fitting the speedo! Peter.
Sender Tubes
Sender Tubes.jpg
Sender Bracket
Sender Bracket.jpg